Upregulation of renal alpha 2-adrenergic receptors is not indicative of salt-related increases in blood pressure in spontaneously hypertensive rats.

Abstract

The aim of the present study was to determine if elevations in salt intake were coupled to increases in renal alpha 2-adrenergic receptors in SHR that differ in their blood pressure response to high salt diets. Salt-resistant spontaneously hypertensive rats (SHR-R), which do not increase their blood pressure in response to high salt intake, and salt-sensitive spontaneously hypertensive rats (SHR-S), which do exhibit significant elevations in blood pressure on high salt diets (3.15% NaCl), were used. Radioligand binding studies using [3H]rauwolscine were performed on 6- and 11-week-old SHR-S and Wistar-Kyoto (WKY) rats to determine the effects of age, strain, and salt intake on alpha 2-adrenergic receptor number and affinity. One week of high salt intake significantly increased blood pressure 22% in 6-week-old SHR-S and increased the blood pressure of 11-week-old SHR-S 12% without altering WKY rat controls. This treatment did not significantly increase renal alpha 2-adrenergic receptors in either SHR-S or WKY rats. SHR-S had significantly higher numbers of renal alpha 2-adrenergic receptors than WKY rats on the high salt diets. One week of high (3.15%) or low (0.05%) salt intake did not significantly alter renal alpha 2-adrenergic receptor number in 11-week-old SHR-S or WKY rats; however, blood pressure was significantly elevated in the SHR-S (175.0 +/- 3.5 versus 196.0 +/- 3.0 mm Hg).(ABSTRACT TRUNCATED AT 250 WORDS)